Rutherford scattering

I have been reading an email thread on the PTNC on Rutherford scattering.

Rutherford scattering is an area I like teaching and feel I have some good story and history to tell of the changing model of the structure of the atom.

The great quote of Rutherford’s being
“the result was as surprising as firing a shell at a paper tissue and having it bounce back.”

I like to discus with students how the structure of the atom leads to the concept that most of matter is empty space (quantum vacuum fluctuations being ignored). I usually raise this idea when teaching scale of the atom, Rutherford scattering and electrostatic repulsion.

The good Mrs. Cotton came towards me the other day talking about how Neil deGrasse Tyson was talking about this and I was pleased to see a participant in the email thread mention that they find it incredible that so many textbooks mention the nature of the atom (being mostly empty space) as though it were just another piece of useless trivia, when it should be used to open up a conversation on, well, just about everything really. I agree with this and most students do enjoy pondering this idea. The priceless quote from Rutherford was this.

The morning after physicist Ernest Rutherford discovered that atoms were mostly empty space, he was afraid to get out of bed for fear he’d fall through the floorboards.

I just thought I must compare the distances between the stars in galaxies involved in galactic mergers and discus with students similarities and differences.

Another participant was asking about citations of Hans Geiger and Ernest Marsden being at the Somme. A great book with some interesting references to this era is Frank Closes “The Particle Explosion” This was what I found.

There are interesting stories to tell of how the physicists were used by their countries in both wars. I also learnt in The Particle Explosion that Rutherford had missed an important meeting, a very serious thing to do.

I watched a great lecture about this which had two demos only one of which I have so far been able to use.

They had a small ball hanging down in the lecture hall and the speaker asked the audience to imagine the lecture hall were an atom, the small ball represented the size of the nucleus. Then he goes on to say no not that small ball, that one is just there to show you were the other one is and there above it was a minute ball barely visible. We now have plastic balls hanging down in most of o7ur labs so that our teachers can demo the same, only given the small size of our labs they point out it isn’t the plastic ball but the o.5mm nylon line supporting it that is to scale.

The other demo was a source aimed at gold leaf with a back scatter detector that rang a bell when it detected something. Periodically throughout the lecture the bell could be heard.

I’d love to recreate this but not sure we have the kit for it. I was thinking about using the MX-10 detector as the screen could be projected up and perhaps students could try and spot an alpha splodge. You really could do with a much bigger detector though.